Operational equipment such as radar and the like transmitting and sensory equipment, is commonly forwardly mounted on an aircraft, e.g. in the nose of the aircraft. The equipment is protected from the environment by a cowling or nose cap assembly which on most aircraft is constructed predominantly from material which is transparent to electromagnetic radiation at the operational frequencies of the equipment. Typically the cowling assembly is made of a fiber reinforced honeycomb structure. Such materials, however, do not provide protection against lightning which can puncture the nose cap assembly and cause severe damage to the electronics or sensory equipment.
For lightning protection, it is known to provide conductive strips on the general external surface of the nose cap assembly. The conducting strips are typically of a material and are of sufficient cross sectional area, to capture a leader channel of the lightning, and conduct it, for example, to the (metallic) air frame, so as to protect the nose cap assembly and the operational equipment behind it. Although the metallic conducting strips are efficient at providing lightning protection, they can interfere with the proper operation of the sensory equipment. For example, where the equipment is radar, the presence of metallic strips can obstruct the radar's view.
It also is known to utilize a lightning diverter strip consisting of metal elements which are insulated from one another. Such a strip may be made virtually, if not completely transparent to electromagnetic radiation under normal conditions. When subjected to high electrical field conditions, as can be experienced if the nose cap assembly is struck by lightning, the material enables an ionized channel to be established along the surface of the diverter strip to divert the attachment point of the lightning arc by extending the arc length along the path above its surface. The use of diverter strips may provide for less sufficient lightning protection than conducting strips of corresponding cross section. However, diverter strips are widely used in order to not obscure the reception of electromagnetic radiation by sensory equipment housed behind the cowling.
Where the cowling is large, such that very long diverter strips would be required to extend along the nose cap assembly external surface from a window position in front of the sensory equipment to the air frame, lightning diverter strips do not offer sufficient lightning protection. While lightning conductor strips could be used in the place of the lightning diverter strips, the conductive strips would then tend to obscure the window in front of the sensory equipment.